But "polite memo" is not how anyone I know would describe this.
Conclusions, particularly conclusions on sensitive subjects, baldly stated without a bunch of qualifiers don't tend to be considered polite.
Sucks, but there it is.
It was a badly structured and badly argued document, and I disagree with most of its factual claims and its policy recommendations. But it in no way was impolite or in violation of Google's code of conduct, unless you think that having that viewpoint inherently makes you in violation and deserving of excommunication.
The reality is impolite is in the eye of the beholder (or culture). And in the Bay Area, that would be considered an impolite way of communicating considering the topic.
I'm not applying a value judgement here.